


Second Law

by gargargarrick



Category: UQ Holder!
Genre: For Science!, Gen, Immortality, Physics, Pyromania
Language: English
Status: Completed
Published: 2014-08-03
Updated: 2014-08-03
Packaged: 2018-02-11 14:49:44
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 783
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/2072349
Author URL: https://archiveofourown.org/users/gargargarrick/pseuds/gargargarrick
Summary: <blockquote class="userstuff">
              <p>“Well, basically,” said Touta, “I thought I should keep up with my studying, since I can’t really go to school anymore.”</p><p>Yukihime nodded. “That’s fine, but it doesn’t explain why you set Tokisaka-kun on fire, at all.”</p>
            </blockquote>





	Second Law

“Well, basically,” said Touta, “I thought I should keep up with my studying, since I can’t really go to school anymore.”

Yukihime nodded. “That’s fine, but it doesn’t explain why you set Tokisaka- _kun_ on fire, at all.”

“I’m getting to that!” Touta fished around in his knapsack and pulled out a hardbound book, which he set on Yukihime’s desk. “I went looking through the Holders’ library and found this.”

Yukihime turned the book over in her hands, examining it carefully. It was old and on the verge of falling apart, coated in dark brown dust (at least, she hoped it was dust), but had once been a textbook. According to the faded lettering on the cover, it was a middle schooler’s physics book.

Forgetting herself, Yukihime cracked a smile. She certainly knew this particular book all too well, although she wasn’t sure how it had ended up in the guild library.

“This is from the pre-magic era, though, isn’t it?” she said casually. “I don’t know how accurate it is.”

“That’s the thing!” Touta gesticulated wildly. It appeared that he had broken a sweat. “There’s one part where they talk about thermo-dynamics, right?”

Yukihime nodded, flipping to the appropriate chapter from memory.

“And then there’s a part about conservation of energy.”

_The law of **conservation of energy** states that the total energy of an isolated system cannot change—it is said to be conserved over time. Energy can be neither created nor destroyed, but can change form. For instance, chemical energy can be converted to kinetic energy in the explosion of a stick of dynamite._

_A consequence of the law of conservation of energy is that a perpetual motion machine of the first kind cannot exist. That is to say, no system without an external energy supply can deliver an unlimited amount of energy to its surroundings._

“Oh dear,” sighed Yukihime, the complete picture beginning to form in her mind.

“It’s saying that it’s impossible for us to exist!” said Touta. He looked very proud of himself for having figured this out.

“Like I said, this is a very old book,” said Yukihime. “They didn’t know about immortals back then…”

“That’s what I thought, too, at first. But then I got to thinking.” Touta peered at the upside-down page and turned back to the introduction. (Yukihime boggled; it was the first time she’d seen anyone read the introduction, herself included.) “It’s not like physics are just something someone made up one day. People believed in it because all the evidence and experiments pointed toward it being real, and no one could find anything that proved it was fake, even though lots and lots of people tried, right?”

“I … _suppose_ you could look at it that way, although it’s a bit more complex than that.”

“Well, what if this is actually right, and we’re wrong about the way immortality works? I mean, I’ve had my head cut off and I survived over a month in a hole without food, so it’s not like immortality is made up. But we haven’t ever tried to, like, test it out systematically! There’s so much we don’t understand about it. So I thought I could be the first _immortal physicist_. Pretty sweet, huh?”

“And Tokisaka- _kun_ ,” said Yukihime, rubbing her temple, “just agreed to help you right away, without learning what it would entail, didn’t he?”

“Yup!” Touta said cheerfully. “It was kind of weird, I guess! Anyway, I figured the easiest way to check if energy was really conserved would be to see if we could just sort of…be on fire, indefinitely. But then Karin- _san_ came and put him out and yelled at me. Now we’ll never know the truth! She’s an enemy of science!”

“Yes, well, about that. In research there’s this very important thing called ‘ethics’. They talk about it in that book, but…part of it is that you _can’t_ just make your subjects be on fire forever without asking, all right?”

“Even –”

“No, _not_ even for science. I’m sorry.”

Touta hung his head, seemingly in contemplation. “I see…so I just have to master ‘ethics’ and I can fulfill my dream! Go science!”

“Wait, um, it’s not as if it’s a kind of martial arts technique…”

He was already out the door. “Kuroumaru! Are you free? It turns out I need more training! Kuroumaruuu?”

Yukihime sighed; he had even forgotten to bring the book with him. _Well_ , she thought, _I suppose people can’t change their nature._ With that, she found herself opening the book again, for nostalgia’s sake.

_People working together to find the truth, was it?_

_Perhaps there’s still some value in science, even in the age of magic._

**Author's Note:**

> Includes text from “Conservation of Energy” on English Wikipedia (https://en.wikipedia.org/wiki/Conservation_of_energy). Licensed under the Creative Commons Attribution-ShareAlike License.


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